Liquid rheostat.



G. I). DORGELOH.

LIQUID RHEOSTAT. APPLICATION FILED JULY 30, 1914'.

1,201,707. Patented Oct. 17,1916.

Witnesses: Inventor:

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GEORGE E. DORGELOH, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

LIQUID REED-STAT.

specification of Letters Patent.

Patented Oct. 17', 1916.

To all whom it may concern:

Be it known that I, Gnonon H. DORGELOI-I, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Liquid Rheostats, of

p which the following is a specification.

This invention relates to rheostats for controlling electric circuits, and especially to a form df liquid rheostat which will be found of peculiar advantage in the operation of induction motors having their rotor windings terminating in collector rings which are to be connected to outside resistances. In this class of work it is desirable to have as great a range of resistance as possible between the starting and running positions of the rheostat and to reduce the final resistance as low as possible in order to minimize the slip-of the motor at full load.-

, One point of weakness in all liquid rheostats heretofore devised has been the low range of resistance, or in other words the low ratio between the initial andthe final resistance values. This defect has been due largely to the fact that the electrodes or plates must be spaced. so far apart to avoid flashing over at high voltage that a low final resistance could not be obtained.

By my invention I am able to obtain a low final resistance and a good range between initial and final resistances. I provide for a wide spacing of the plates and a consequent high resistance during the initial operation of the device when the voltage is high, and a smaller spacing of the plates when the voltage is low during the final operation.

In that embodiment of my invention which forms the subject matter of the present application, there is a set of main electrodes and one or more sets of auxiliary electrodes, the forme first and the latter afterward. The-auxiliary electrodes are movable toward and away from the main electrodes, so that the resistance between any two plates can be varied. The auxiliary plates are not immersed during the first stage of'the operation, but they are immersed in the final stage, and since they and the main plates are-conbeing connected in circuit nected in parallel to the leads running to the collector rings on the motor, the final resistance is very low.

The accompanying drawing shows in diagrammatic form an embodiment of my invention.

The induction motor M is the one which is to be controlled. The collector rings 1 of this motor are connected by conductors 2 to a. plurality of plates or other electrodes 3 4 and 5 hanging in a chamber 6 which is in closed in a tank R. The main plates3 are preferably few in number and of considerable length, so that their lower ends dip below the level of the liquid in the chamber 6 at all times. The main intermediate plates 4 do not depend so deeply into the chamber and are greater in number than the plates 3. The auxiliary plates 5 are shorter than the intermediate plates 4 and there are more of them. They are all mounted on a common support such as the rod 7 which is movable lengthwise of the tank, transverse to the planes of the.plates. Flexible conductors 8 connect the, auxiliary branch conductors which connect the plates 3, t to the conductors 2.

In one end of the chamber 6 is ing, the height of whose sill 9 bottom of the chamber determines of the liquid therein at starting. This opening is controlled by a gate or weir 10, preferably carried on rock arms 11 1 voted at 12 and capable of oscillation by an arm 13, link 14: and pivoted lever 15. A sector gear 10 on the hub of the lever meshes with a pinion 17 on the shaft of a controller C. When the lever is thrown over to turn on the current, it also lifts the weir, which causes a rise of the water level in the chamher 6. A pump P driven by an electric motor M takes liquid from the tank R and delivers it constantly to the chamber 6, the overflow running back into the tank so that the liquid is continuously circulated, and the heat is kept down.

an openabove the the depth plates 5 with the Current is supplied to the three-phase I ling the circuit of the other. When the controller C is turned to the first forward position f and the switch S closed, the winding of the contactor 18 will be energized by current flowing from the phase .a through the contacts on the controller and the interlock 21 on the contactor 19, and

back to phase 6. This will close the primary circuit of the motor M, and since there is some liquid in the bottom of the chamber 6 the secondary circuit will be completed through the high resistance af- ,the motor will decrease until .the liquid reaches a height determined by the position of the upper edge of the weir, over which it then flows to the tank. For the first position of the controller, the weir stands at such. a height that the liquid does not wet the plates 4. Further movement of the operating handle moves the controller to the position f and will raise the weir to such a point that the liquid will rise and first immerse the plates 4 and finally the auxiliary plates But just before the plates 5 are immersed, the liquid rising in a tube at one end of the electrode chamber submerges the contacts 23 and closes the circuit of a solenoid 24 whose core 25 is attached to the rod 7. The energizing of the solenoid pulls all the auxiliary plates 5 into close proximity to the main plates 3 and 4, so thatthe resistance of the liquid which presently rises between them is greatly reduced.-

' The voltage being now much lower, there is no danger of arcing across between the plates. The result is a very low resistance in the final position; much lower than would be possible with the main plates alone. The ratio of resistance of the apparatus is therefore increased, while the slip losses of the motor are reduced.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is onlyillustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States. is

l. A liquid rheostat for electric circuits,

' and arranged to be closedby the liquid when between said electrodes when the auxiliary electrodes are immersed.

2. 'A liquid 'rheostat for electric circuits, comprising main electrodes, auxiliary electrodes immersed after the resistance has been lowered, and means for moving the latter into closer proximity to the former when immersed.

3. A liquid rheostat for electric circuits, comprising stationary main electrodes, a

movable support, auxiliary electrodes carried 7'5,

thereby, and means for automatically moving said support just before said auxiliary electrodes are immersed.

4. A liquid rhecstat for electric circuits,

comprising stationary main electrodes, a

sliding rod, auxiliary electrodes carried on said rod, a solenoidfor actuating said rod, and meansfor energizing said solenoid when the liquid rise "to a predetermined height.

5. A. liquid heostat 'for electric circuits,

comprising stationary main electrodes, a sliding rod, auxiliary electrodes carried on said rod, a solenoid for actuatingsaid rod, and contacts in circuit with said solenoid it rises'to a predetermined height.

6. A liquid rheostat for electric circuits, comprising a few main electrodes, a large number of intermediate electrodes an auxiliary electrode for each main anr. intermediate electrode and means for automatically bringing said auxiliary electrodes into close proxiunty to the others.

7. A liquid rheostat for electric circuits comprising main electrodes for varying the resistance, auxiliary electrodes connected in parallel with the main electrodes and immersed after the resistance has been lowered and means for lessening the space between each main electrode and the auxiliary electrode associated with another main electrode when the auxiliary electrodes are immersed. 8. A liquid rheostat'for electric circuits comprising main electrodes for varying the resistance, auxiliary electrodes connected in parallel with the main electrodes and immersed .when the resistance approaches a minimum, and means for lessening the space between each main electrode and the auxiliary electrode associated with another main electrode when the auxiliary'electrodes are immersed.

9. A liquid rheostat for electric circuits comprising main electrodes for varying the resistance, auxiliary electrodes connected in parallel with the main electrodes and immersed when the resistance approaches a minimum, and electromagnetic means for lessening the space between each lain electrode and the auxiliary electrode associated with another main electrode when the auxiliary electrodes are immersed.

10. A liquid rheostat comprising a tank,

main electrodes therein, means for causing with another main electrode when the auXilliquid to rise in said tank to reduce the reiary electrodes are immersed. 1,0 sistar v, auxiliary electrodes connected in In Witness whereof, I have hereunto set parallel with the main electrodes and immy hand this 29th day of July, 1914'.

mersed when the resistance approaches a GEORGE H. DORGELOH. minimum, and means for automatically les- Witnesses:

. sening the space between each main elec- BENJAMIN B. HULL,

trode and the auxiliary electrode associated HELEN ORFORD. 

